As for the specific tag questions I would recommend you contact OSIsoft technical support (firstname.lastname@example.org or this link for your local support phone number) as sthey are much better equipped to answer such questions.
For general programming questions you can see this great vCampus exclusive webinar on PI Programming 101.
@Eileen Stetter: have you found the answers to your questions?
As Ahmad pointed out, you can contact our regular technical support team for administration/configuration questions such as the Performance Equations (PE) formula you posted in your original post. I am sure other people here on this community could help, but the focus being on development and integration of PI with other systems, your best bet is to contact regular tech support.
As for your question about referencing a tag in "Visual Basic Application/Visual Basic Editor", it definitely seems like a programming question so we should be able to assist you Where is it exactly, that you want to be developing Visual Basic for Applications (VBA) code... in PI ProcessBook? in Microsoft Excel?
Please tell us what you need to do and we'll point you in the right direction.
Yeah I figured it out! Thanks for your help!